I feel like there really hasn't been sincere data-backed methods with proper resources behind them, for example governments giving out minor cash benefits to parents of a few thousand dollars when that's a drop in the bucket compared to the total cost of raising a kid and is not going to convince anyone who wasn't already going to have kids.

Also, that's a wild solution. You'd have to do away with monogamy which would cause some pretty insane societal shifts. However, as a straight guy I can see the appeal lol.